Additive manufacturing (AM), also known as solid freeform fabrication or 3D printing, refers to a manufacturing process where three-dimensional objects are built up from successive dispensing of raw material (e.g., powders, liquids, suspensions, or molten solids) into two-dimensional layers. In contrast, traditional machining techniques involve subtractive processes in which articles are cut out from a stock material (e.g., a block of wood, plastic, composite or metal).
A variety of additive processes can be used in additive manufacturing. Some systems use an energy source to deliver energy to feed material, e.g., a powder, to sinter or melt the feed material. Once all the selected locations on the first layer are sintered or melted and then re-solidified, a new layer of feed material is deposited on top of the completed layer, and the process is repeated layer by layer until the desired article is produced. In many of these methods, the energy source is a laser that emits an energy beam to fuse powder to form an article. Some laser-based methods melt or soften material to produce layers, e.g., selective laser melting (SLM) or direct metal laser sintering (DMLS), selective laser sintering (SLS), fused deposition modeling (FDM), while others use energy beams to cure liquid materials using different technologies, e.g. stereolithography (SLA). These processes can differ in the way layers are formed to create the finished objects and in the materials that are compatible for use in the processes.